Mechanism poly photodegradation reactions

The mechanism of photodegradation can be presented by the following reactions, using as an example poly(p-ethylstyrene) (3.88) [2258] ... 

The chemistry of the oxidative and nonoxidative photodegradation of poly(vinyl chloride) is reviewed with emphasis on work that has been published since the early 1970 s. Topics covered include the nature of the photoinitiating species, the photoinitiation mechanism, and the structural consequences and reaction mechanism of the overall photodegradation process. Also included is a summary of recent studies on the determination of structural defects in poly(vinyl chloride) by carbon-13 NMR. 

Photodegradation of poly(a-methyl styrene) through a charge-transfer complex with tetracyanobenzene has also been described [1160]. A tentative mechanism for this type of photodegradation may be presented by the following reactions ... 

As mentioned previously, the exposure of poly(vinyl chloride) to either ultraviolet light or heat leads to degradation, as a result of which discoloration and changes in mechanical properties can occur. The degradation of poly(vinyl chloride) has been the subject of extensive investigation and much information has accumulated. However, the reactions which take place are complex and are not completely understood at the present time. Whilst thermal degradation and photodegradation of poly(vinyl chloride) have much in common, they are distinct processes and are considered separately. 

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